Title: Good Mutation or Bad Mutation? Humans and Malaria
Lesson Overview
This lesson will be using some concepts learned from the unit on Mendelian genetics. Students will be learning the story of how the presence of Malaria in Africa has led to the recurring presence of a "bad" gene - the gene for sickle-cell anemia. This story vividly illustrates how evolution and genetics are inextricably linked together. Without the presence of malaria, the process of natural selection would definitely be selecting against the sickle-cell mutation and it would have been eliminated from populations long ago.
Objectives
The student will recognize and explore links between Mendelian genetics and evolution / natural selection. The student will explore the possibilities of mutations - that while some may harm the organism, others may be beneficial. The student will identify environment as the major component of determining an organism's fitness.
Materials
Science Journals
Allele cards marked N and S
Activity packets:
The instructor will open the class as usual with a journal prompt that reads, "Is genetic diversity in a human population a desirable thing? Why or why not?" After the class is settled and attendance is taken, the instructor will lead a short discussion of the prompt with the class.
Learning Activities
The instructor will then open up an online video that describes the plight of malaria victims in Africa. It explains how malaria works, by introducing a parasite that infects red blood cells and makes them burst, which can cause death. It then explains the sickle-cell trait that many Africans carry. A homozygous condition for the sickle cell trait will result in an individual acquiring sickle-cell anemia, which can make life painful and difficult without treatment. A heterozygous condition for the sickle cell trait actually confers resistance to the malaria parasite - therefore one copy of this gene is actually beneficial to survival. A homozygous condition for normal (non-sickle) blood cells means that the individual will not have sickle-cell anemia, but they are vulnerable to infection and death from the malaria parasite.
The instructor will then begin a class activity in groups. An activity packet will be handed out to each individual student. The students will be divided into groups of 8. Students will each receive a random pair of allele cards that are either marked with an 'N' or an 'S'. 'N' will represent an allele for normal blood cells and 'S' will represent an allele for sickle blood cells. The number of individuals who exhibit each pair of alleles will be written down in the packet. Students who receive 'SS' will be removed from the group populations. Then two remaining students will be chosen at random to create the next population, and their alleles will be used in a Punnett Square to calculate the probabilities of the frequency of alleles in the next generation. One student will create allele pairs in the proportions calculated by the square, and the students in the group will pick up a random pair of cards. Once again, "SS" are removed from the population and the process repeats to create a third generation. Generation 3 is then struck by malaria, eliminating both "NN" and "SS" individuals from the population. The number of surviving individuals is recorded once again, and then the students will briefly answer the discussion questions in the packet.
Closing
The instructor will close the lesson by going over the answers to the discussion questions with students. the instructor will remind the students: "While this activity was a simulation for the class, for many people around the world these kind of forces exert impacts on their everyday lives. Therefore, human evolution is not finished! During the next class period we'll discuss and work with the implications for the future of human evolution."
Assessment
Formative assessment will be conducted by observing student responses to the journal prompts. The instructor will also circulate around the room during the activity portion to check for understanding and ensure that the students are completing the activity correctly. Summative assessment will consist of the instructor checking the activity packets for correctness, and the discussion questions for conceptual understanding.
Unit: Human Evolution
Title: Good Mutation or Bad Mutation? Humans and Malaria
Lesson Overview
This lesson will be using some concepts learned from the unit on Mendelian genetics. Students will be learning the story of how the presence of Malaria in Africa has led to the recurring presence of a "bad" gene - the gene for sickle-cell anemia. This story vividly illustrates how evolution and genetics are inextricably linked together. Without the presence of malaria, the process of natural selection would definitely be selecting against the sickle-cell mutation and it would have been eliminated from populations long ago.Objectives
The student will recognize and explore links between Mendelian genetics and evolution / natural selection.The student will explore the possibilities of mutations - that while some may harm the organism, others may be beneficial.
The student will identify environment as the major component of determining an organism's fitness.
Materials
Science JournalsAllele cards marked N and S
Activity packets:
Links to Resources
Video on malaria and sickle-cell anemia: http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.htmlSafety Issues
None.Instruction
Opening
The instructor will open the class as usual with a journal prompt that reads, "Is genetic diversity in a human population a desirable thing? Why or why not?" After the class is settled and attendance is taken, the instructor will lead a short discussion of the prompt with the class.Learning Activities
The instructor will then open up an online video that describes the plight of malaria victims in Africa. It explains how malaria works, by introducing a parasite that infects red blood cells and makes them burst, which can cause death. It then explains the sickle-cell trait that many Africans carry. A homozygous condition for the sickle cell trait will result in an individual acquiring sickle-cell anemia, which can make life painful and difficult without treatment. A heterozygous condition for the sickle cell trait actually confers resistance to the malaria parasite - therefore one copy of this gene is actually beneficial to survival. A homozygous condition for normal (non-sickle) blood cells means that the individual will not have sickle-cell anemia, but they are vulnerable to infection and death from the malaria parasite.The instructor will then begin a class activity in groups. An activity packet will be handed out to each individual student. The students will be divided into groups of 8. Students will each receive a random pair of allele cards that are either marked with an 'N' or an 'S'. 'N' will represent an allele for normal blood cells and 'S' will represent an allele for sickle blood cells. The number of individuals who exhibit each pair of alleles will be written down in the packet. Students who receive 'SS' will be removed from the group populations. Then two remaining students will be chosen at random to create the next population, and their alleles will be used in a Punnett Square to calculate the probabilities of the frequency of alleles in the next generation. One student will create allele pairs in the proportions calculated by the square, and the students in the group will pick up a random pair of cards. Once again, "SS" are removed from the population and the process repeats to create a third generation. Generation 3 is then struck by malaria, eliminating both "NN" and "SS" individuals from the population. The number of surviving individuals is recorded once again, and then the students will briefly answer the discussion questions in the packet.
Closing
The instructor will close the lesson by going over the answers to the discussion questions with students. the instructor will remind the students: "While this activity was a simulation for the class, for many people around the world these kind of forces exert impacts on their everyday lives. Therefore, human evolution is not finished! During the next class period we'll discuss and work with the implications for the future of human evolution."Assessment
Formative assessment will be conducted by observing student responses to the journal prompts. The instructor will also circulate around the room during the activity portion to check for understanding and ensure that the students are completing the activity correctly. Summative assessment will consist of the instructor checking the activity packets for correctness, and the discussion questions for conceptual understanding.Homework
None.Additional Notes
None.